Invited Review: Methods to Determine Body Fat Reserves in the Dairy Cow with Special Regard to Ultrasonographic Measurement of Backfat Thickness

Abstract

As the dairy cow uses body energy reserves in early lactation,bodyconditionscoringhasbecomeanintegral part of dairy herd management. Several methods based on visual and tactile evaluation have been developed. Problems caused by the subjectivity of these techniques have been reported. Alternative approaches to predict energy reserves or energy balance in dairy cattle in- clude metabolic profiling and measurement of live weight, heart girth, or skinfold thickness. A less com- mon method to assess fat reserves in body tissues is measuring backfat thickness (BFT) by using ultra- sound. An ultrasound technique has been established to predict carcass quality in beef cattle. A new aspect is the application of ultrasound as a monitoring tool in dairy herd management where another location has to be evaluated. This technique has been validated by relatingBFTto totalbodyfat(TBF)content andcarcass BFT. Backfat thickness also has been related to other methods ofbody condition scoring.Target valuesfor the developmentof BFTthroughout lactationare available. The relationship between BFT and TBF content is highly significant although biased by multiple factors. A change in BFT of 1 mm equates to approximately 5 kg of TBF content. Measuring BFT by ultrasound is of added value compared with other body condition scor- ing systems because it is objective and precise. Changes in body condition can be detected and evaluated properly.